The disposal of waste material of domestic, commercial and industrial character is an extremely troublesome area of activity. The most dangerous types of waste material encountered in shredders include: discarded cans used to contain gasoline, clean fluids and the like; various spray cans containing a propulsion medium under pressure; metallic materials that create sparks which can ignite dust; and aluminum filings (thermite) which burn without external oxygen and are explosively dangerous.
In the operation of some shredders it has been the practice at times to locate personnel adjacent the feed conveyors to scan the material and pick out the kind of waste materials noted above which can be the cause of an explosion. This is a critical area for people to occupy. Where a high volume of the waste is made up of garbage, paper, wood and items of that character which are not easily shredded if containing more than normal moisture, it has been the practice also to enclose such shredders in structures to keep the material out of rain and snow conditions. When explosions do occur, the shredder is likely to sustain severe damage and the structure surrounding it can be blown apart, with consequent chances of injury to people by flying objects.